Treatment of plaster of paris.



' all whom it may concern certain new and 'hseiful Improvements in the Treatment of PlusterofPm-ls, of which other forms of solutions or chemical equivalents which perform the some or arsim llma.

' in its uses.

,tungstate "of ca'l'cium formed by combimiQ tion. of the calcium of the plaster of Pans tial to-the combination.

I In carrying out my process I- prefer to e'mp'loyn saturated solution of sodium tung- The particular form of sodium tungstate calcium sulfate of the hardened plaster of;

ch lly mentioned it as 'a' preferred chemical: solution in the exemphficat lon or disclosure I UNITED ATES;

up rnUEMAN Buns 0F NEW YORK, N. Y.

lnnm'mnnr 0F PLASTER or PARIS.

Ifl'o Drawing.

;Be it known that I. HA'L TRUESIAN Bums. an citizen ofthe United States, and a resideu tio'f the city of New York, in the county of New York and State of New York; United States of America, have invented the following is aspecification;-

My 'nvention relates "to ,a process ii method of trezit'i'ng plaster of Paris Wheref by its hardness is increased, itflis rendered" water-proof, and is'm'ade susceptible tohigh polish. Such qualities "imparted 'to lilo-ck for forms of pl zister-of Paris render it peculia-rly suitable for the replacementof stone I will describe my invention in the following' specification 4 and point out th'e noi'e'l features thereof in the appended claims.

Broadly, my invention resides in produ'c ing on the pl aster of Paris a surface of h 511011 soluble tuugstntes as are ssenustate which has been renderedstrongly 211- kalin'e, as, for exm'uple, by means of ammonia.v This solution is applied to the surface of the hardened or set? plaster of Paris and the surface rubbed with a cloth or other suitable materizi-l, or otherwise burnished until dry. A second application of the so- 1 dium tungstnte solution is then made and the process repeated until the desired coatin or surface has been produced.

he concentration of the sodium timg-- st atesolution may he varied if desired.

solution hereinbefo-re set forth seems best adapted to the formation of the coating of calcium tungstute whichv is produced during the process by chemical reaction with the Paris, and for that-reason I have specifiof; my invention herein described, (although function aire Specification 0! better: I'atent Patented Oct. 1913.; linilieatifimfiled twin-1e11,- seminal-moss. 1 I

. I well within the scope of my invention. y

I have s'thted that the compound fornhklu by my process is 'a mngsmte of .c'al'ciu i Broadly; however, my invention, i'nclm v the idea of producing n 'chinic'al change in calcium sulfate by afpifilyi "f'thereto slitr" stances which produce a chemical reaction therein to 'form a tun 's t'it or zinalogrius'f compound. For e'xmnb ems il'iclif c'zit-ing ow lines of substitution of d ilferem components in the practice of my ,pj rocess, it is tolx. noted that chemically in oly -bde'nu in is m'xiihz like tung'state in main} of. compounds it! pro lnces, have hand] it feasible to nse' sodi-um molybdgite in placeof sodium tungstate. The calcium molybdrtc is in every way analogous to "the calcium lt-un%state,

and, owing to this marked chemical and physical similarity, comes within this invention. I hare used, with s'imilhr-results, ammonil'lm t'un'gstate, pot-fissium ttmgnstnte. sodium molybdate; po tns'sium -molybda-te. 5 and ammonium inolybda te.

The other essential com-boom for the production of the compouho f my process is calcium sulfate, and byjthe term of plaster Tof Paris used herein "I mean 'to include rill 8o 1tho'se forms of calcium "s'il il ftite -which-haye Joeen produced'by first dehydrating crystal! lized 'colcium sl'ilfate or'f psumandihen tillowing the same to set hither ivith 'W-nter alone or with \i'ot'erin combinationQBb with the venous hardening agents used for I this purpose.

rrepea-te applications g t I What I claim is 5- 1. The, process which comprises the cone version of the surfaic of crystallized -cal-. ciun'i sulfate into calcium tungstate by the state in solution.

combination. therewith of'a sohible tung- 2. Thelprocess which comliriscsj-the pro duct-ion of a hard wate calcium ti'ingstate or its st-hntial equivalent o'n hardened p'les't of Psris 'b the Y chemical interaction there 1 v,-i't-h if; so ution' of sodium ,t-ungs'to tc or its suhsth ritifil equiv gi-leno. n v p I 3. The process of treating pla ccrvot Paris tht consists in setting-the pla ster'of Paris; into a solid mass of'desired shapefinakipf o f'a solution of an alkaline tungsfate adaptname to this specification in the presence. of

to combine directly'with the cfalcium sultwo subscribing witnesses. ate to produce a coating or sur ace of 0111- v cium tungstate,-and burnishing the coating HAL TRUEMAN 5 or surface between each application to dry Witnesses:

and polish the calcium tupgstate; Clams F; CLAAR, H In testimonywhereof I heve signed my FRANK C; Elm. 

